The present invention generally concerns a method and apparatus for packaging individual articles or products, and more particularly for packaging such items (or stacks thereof) in plastic-type wraps or films without any tension in such films.
In general, machines which utilize some form of continuous web of film for wrapping articles are well known. One category of such machines forms a tube from a continuous web of film, draws the film over a collar for actually forming such tube, and then provides an overlap seal at a desired joint. Products to be wrapped enter the tube continuously at spaced apart intervals. Since such machines utilize a collar-type assembly for forming the tube, or some type of folding frame work to achieve closure of a given package, such collar or frame work must be physically adjusted or interchanged with another before the machine can be used for making different sized packages, or even handling different size products.
A number of U.S. patents have issued concerning various packaging processes and devices, with the following list being only a brief representative list of same to serve as additional background information for the reader:
______________________________________ U.S. Pat. No. INVENTOR(S) DATE OF ISSUE ______________________________________ 4,463,542 Greenawalt et al. August, 1984 4,152,880 Kolosov et al. May, 1979 4,041,673 Brooke et al. August, 1977 3,914,917 Young October, 1975 3,596,428 Young August, 1971 3,382,644 Vogt May, 1968 3,097,462 Langdon July, 1963 ______________________________________
In addition to the above-described tube-type formation, it is known to encase individual products between separate upper and lower webs of film, which films are subsequently sealed together in various manners so as to form a finished package. U.S. Pat. No. 2,931,148 issued to A. M. Smith on Apr. 5, 1960 is an example of one such device using thermoplastic materials such as polyethylene films, which are subsequently heat sealed.
One problem when sealing products between a pair of films is that the sealing mechanism (often including some type of moveable bar) may rupture the films during sealing, or induce undesirable tension therein resulting in later damage or failure. Also, joining a plurality of separate webs of film often results in a finished package having unsightly or undesirable seal joints. Even the tube-type approach referred to above can result in a final package having an overlap seal on the top or bottom of the package.
Not only are poor seal formations aesthetically unappealing from a marketing standpoint, but many applications require the ability to legibly print on the resulting packaged product. For example, phonograph records, games, models, or the like would in general be undesirably packaged if it were impossible to legibly print on the finished package, or if printed subject matter on the products themselves were obscured by folded over layers of plastic wrap. Other types of less structured (i.e. less stiff) products, such as towels, pads, or the like do not provide sufficient stiffness to be fed into a collar of the collar-type machines, or are otherwise not suitable for reliable handling by conventional packaging machines.
Frequently, it is desireable while forming a package to also compress the enclosed products; however, many conventional packaging machines do not possess such a capability. For example, towels are one product which are preferably compressed at least for purposes of packaging and/or shipment. U.S. Pat. No. 3,837,138 issued to R. D. Terry on Sept. 24, 1974 discloses in general a method and apparatus for compressing a compressible material, such as a batt of insulation, while simultaneously packaging such product.
While the option of compressing products as they are being packaged is often desired, it is frequently even more desireable to provide a completed package formed with at least tensionless film. U.S. Pat. No. 4,313,288 issued to Tassi et al. on Feb. 2, 1982 generally discloses a reciprocating carriage member which is operative in association with an upper sheet pay-off drum so that a web of wrapping material is suitably drawn off of a storage roll, whereby articles of different tallnesses may be sealed without undue sheet tension.